The human brain is a vastly complex and remarkable creation of biological engineering. To give an idea of just how vast, one only needs to consider that if its 100 billion nerve cells, or neurons, were laid out end-to-end, they would measure 1000 km and, while only comprising 2% of average body weight (1.3-1.4kg or 3 lbs), it consumes fully 20% of the oxygen and calories we take in. Furthermore, each one of these neurons are able to change form and re-organize themselves, which at the cellular level is called synaptic plasticity, and cortical remapping when comprising vast numbers of nerve cells, at a brain-wide scale. The catch-all term for the brains physiological changes is Neuroplasticity.

The process of neuroplasticity occurs when there are changes in the levels of stimulation to the brain, whether in response to learning new skills, forming memories or adapting to injury. The mechanics of these changes play out when neurons reach out to connect with others, forming entirely new pathways. Like a single file on a computer, a pathway ‘records’ a single memory, to be retrieved later, when necessary. The more often this ‘file’ is retrieved, the easier it is to retrieve. Whether it is learning to solve a particular mathematical problem or playing the piano-practice makes perfect, as practice strengthens the usability of that ‘file’. However, the opposite is true when practice, or use, is culled from routine: nerves retract from each other and pathways wane. Though the biology and processes are quite different, one can, with a bit of ‘poetic licence’, loosely compare this process to how muscles redefine themselves, from the labours of exercise or dwindle through inaction. It is not uncommon for individual neurons to connect with over 100,000 others, with a total of 100,000,000,000,000 (100 trillion) connections throughout the brain.

Regardless of lifestyle, health or favourable genetics, the inescapable process of aging has us losing our hearing by a ½% per year. As a result, older adults must concede that their ability to comprehend, especially within noise, will require more effort, than for younger adults or children, even though they may share identical hearing test results. (Gordon-Salant, 2005; Souza, Boike, Witherell, & Tremblay, 2007) This age-related haring loss is called presbycusis, and can be cultivated from both biological and cognitive sowings. Cognitive presbycusis is said to be Central, when the auditory centres in the brain begin to lose their ability to process complex sounds, such as music and speech, as a result of diminishing cognitive abilities. (American Academy of Audiology Task Force on Central Presbycusis, 2012) Biologically presbycusis occurs when the neurons are less able to repair themselves: sound receiving cells within the cochlea, or inner-ear, are less receptive to sound, due to the effects of noise damage and the neurons themselves ‘misfire’, for example. Both forms are most disquieting to those struggling with conversation, which is only exacerbated in noise.

Understanding the fundamental processes which cause reduced understanding abilities, alongside hearing loss, are paramount to effectively rehabilitate, as much as possible, the hearing loss and communicative difficulties. The end goal should be meaningful hearing: that which is bound to increased speech discrimination and environmental awareness, and not merely amplification. Improperly chosen or poorly performing hearing aids may only act to increase quiet garble into loud garble. Although absolutely crucial, hearing aids are only one part of the equation, as the sense of hearing is tightly interwoven with areas of the brain which are responsible for vision, memory, learning and, in general, the ability to think clearly: to affect one, is to affect all. Over the last two decades much has been learned regarding the ties between hearing loss and other brain functions. Numerous research projects, carried out by universities, government-sponsored agencies and medical centres, have all clearly linked longstanding unaided hearing loss to Alzheimer’s, cognitive impairment, depression, reduced health and quality of life. Some of the more notable findings clearly link a 300% increase in the rates of Alzheimer’s in individuals with unaided hearing loss, greater than or equal to moderate levels. (Dr. F. Lin, Johns Hopkins University, 2014; Dr. A. Wingfield, Brandeis University, 2014; NIH, 2014, etc.)

With unaided hearing loss, the amount of signal getting to auditory centres is reduced; this reduction in the customary amount of ‘acoustic exercise’ acts to weaken the pathways, as neuron-to neuron connectivity wanes.

The genesis for Alzheimer’s is initiated through a complex mechanism of changes to the brains larger-scaled pathways, called cross-modal cortical organization, or cortical re-mapping. In this case, one section of the brain ‘hijacks’ neurons from another.

The results are significant and all-consuming:

Increased rates of Alzheimer’s/dementia: under-utilized auditory neurons are, in part, taken over by areas which process vision and touch. In turn, these now ‘neuron-hungry’ auditory centres seek out and commandeer neurons which are normally dedicated to the higher brain functions of reasoning and decision-making. As well, the ability to form short and long-term memories, as well as working memory, which is instrumental in performing on-the-spot tasks, if also negatively affected. (Sharma, et al., 2015)

In part, hearing loss forces one to ‘work harder’ to hear, with an ever increasing reliance upon speech (lip) reading and visual cues. Acting like a distraction, the coping techniques for ‘better’ hearing reduces the ability to absorb information. The brain can only process a limited amount of information, at any one given time, which is referred to as cognitive load. With more of this load devoted to hearing, less is then available to learn, think and memorize; with the latter being accomplished through retention and repetition. In same manner that repeated animal crossings tamp out a pathway in a meadow, so too does repeated ingestion of like-information lead to the creation of pathways (or files) acting to store information within the brain.

Phonemic regression: a reduction in the ability to understand speech, which is well out of proportion with the degree of hearing loss. Even though words are fully audible, comprehension is reduced, sometimes drastically. It is a case of ‘if you don’t use it, you lose it’.

Social isolation and depression: reduced communication abilities may lead to feelings of frustration, exclusion, feeling teased or mocked. Reactions may include annoyance, embarrassment, withdrawal, anger and paranoia. (Dr. D. Myers, Hope College, 2015) Hospital stays and accidents also increase, in part due to unchecked health problems, from reduced contact with friends or family.

OK, enough gloom-and-doom…so what do we do? Turning-back-the-clock, hasn’t been invented, so we must proceed with alternate strategies to ‘turn back’ the undesirable effects of neuroplasticity, as direct result of hearing loss.

To do so takes willpower and attention from ‘both sides of the ears’: those who listen through them and those who speak into them. It is important to note that those with hearing loss are ALWAYS unaware of how much they are actually missing. If you miss something, but were not aware of it in the first place, then you can never know–truly-what you’ve missed. Example: Two people are in one room, when a timer ‘beeps’ in another room. Person ‘A’, with normal hearing, comments on the timer, whereas person ‘B’, with hearing loss asks, “what timer”? As with any sense, if you can’t detect, for whatever reason, then you can’t be aware.

Seeking out the appropriate healthcare provider(s), to properly identify the root problem, usually begins with family, friends and physicians and hearing health providers. All parties involved have their respective specialties: family and friends will be most in tune with subtle behaviour changes, whereas physicians and hearing health providers, whom are trained to care for and appropriately refer to others within the medical field. In general, common sense is always the starting point for appropriately measured healthcare.

If it is hearing loss, then consider (unlike vision loss) that this can be a sensitive subject with many people. Whether it is found within popular culture or simple interpersonal contacts, it is uncommon for vision problems to be addressed with anything other than sympathy, whereas it is often not the case with hearing loss. In movies and TV, those with severe vision problems are often portrayed as having greater awareness, perhaps even elevated intelligence, whereas with severe hearing loss, it is usually the opposite. One example that comes to mind is from the Carol Burnet show, where one of Tim Conway’s characters exaggerated his appearance of stupidity by by wearing a massive hearing aid and ‘comically’ mixing up what is being said. That same 'shtick' would not be funny if the blind tripped over objects.

Lastly consider the fact that -for those with longstanding hearing loss- use of hearing aids have been proven to increase their chances of a longer lifespan and better physical, emotional and cognitive health.

An excellent article which I hope can be shared with the Alzheimer's Society. It is important that hearing aids be introduced early in a dementia process while the person still has the skills to adapt to using an assistive device

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Ian Murray has been in practice as a Hearing Instrument Specialist since 1993.

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